For the preparation of abhesive coating compositions, it is known that organosilicon compounds which have olefinically unsaturated groups may be reacted in the presence of platinum catalysts with organosilicon compounds which have SiH groups. For example, German Patent No. 29 18 254 describes such a process in which, as organosilicon compounds having olefinically unsaturated groups, those compounds are used which contain at least one group of the formula ##STR2## in which R represents methyl, ethyl or --CH.sub.2 OCH.sub.2 --CH.dbd.CH.sub.2 in the average molecule.
Preparations which contain such organosilicon compounds with olefinically unsaturated groups and organosilicon compounds with SiH groups in addition to platinum catalysts do not have an indefinite shelf life.
From German Offenlegungsschrift 27 03 605, a curable organopolysiloxane preparation of increased shelf life is known which comprises an organopolysiloxane with at least two vinyl groups linked directly to the silicon atoms of a molecule, an organohydrogenpolysiloxane with at least two hydrogen atoms linked directly to the silicon atoms of a molecule and a platinum catalyst, wherein
(a) the organopolysiloxane has the following average unit formula ##EQU1## in which R represents the same or a different univalent hydrocarbon group without an aliphatically unsaturated radical, "a" has a value of 0.00025 to 0.5 and "b" a value of 0.75 to 2, with the proviso that the sum of "a" and "b" is 1.25 to 2.25,
(b) the organohydrogenpolysiloxane which has no aliphatically unsaturated radicals is provided in such amounts that 0.5 to 4 hydrogen atoms which are linked directly to silicon atoms are provided per vinyl group in component (a) and that the composition
(c) has an alkinyloxy group-containing organopolysiloxane which, in one molecule, has at least one univalent hydrocarbon group with a C.tbd.C bond which is linked over an oxygen/silicon bond to the silicon atom.
The essential characteristic feature of this German Offenlegungsschrift 27 03 605 thus consists therein that, due to the presence of an alkinyloxy group, the premature curing of the preparation is avoided, the rapid curing of the preparation at elevated temperatures not being affected.
However, it has proven to be disadvantageous that the alkinyloxy groups containing organopolysiloxanes either are incompletely bonded into the polymer formed on curing or that, in the case of their addition, compounds with allyloxy groups may be formed which are relatively unstable hydrolytically.
The organopolysiloxanes with alkinyloxy groups which are not incorporated in the polymer structure, as well as compounds set free by hydrolysis, migrate to the surface of the coating and impair the suitability of these cured coatings as abhesive coatings.